[The Following is an excerpt from a letter to Allen Meece]
[Updated 6 September 2002]
In an earlier message, I said that the massive tankage
required was an argument against the use of electrolysis for production of
oxygen from water. As it turns out, while the system must still be more
massive than one which uses a liquid oxygen reserve and batteries instead of gas
tanks and fuel cells, the 24 hour oxygen reserve required does not have to be
stored as compressed gas. Since we may rarely if ever need to tap the
whole 24 hours worth of oxygen, only an hour or two worth of oxygen need be
stored as directly accessible compressed gas. The remaining
reserve of oxygen can be stored locked up in pyro-canisters of solid
oxidizer like the emergency oxygen system of a passenger jet.
The complete mass of such a system would be several dozen
times the mass of the oxygen evolved, around 100kg, and would leave behind a
fair amount of byproducts. However, that is still a lot less than the half
ton of tankage required to store the gas compressed. The
pyro-canisters can be used individually, store for years, are more reliable, and
are invulnerable to leaks. The reserve oxygen system need not even connect
to the electrolysis system. The entire reserve supply can be
carried on the elevator, as can its waste products.
Electrolysis fed oxygen systems are thus possible
for less than 1000kg so long as one does not expect the entire 24 hour supply
stored in the same form.
